Preparation of bromine-containing aromatic compounds and their application as flame retardants

ABSTRACT

The invention relates to compounds of the formula Ar(—CH 2 C 6 Br 5 ) y , wherein Ar indicates a structure comprising one or more six-membered aromatic ring(s) and —CH 2 C 6 Br 5  indicates a pentabromobenzyl group, characterized in that at least one carbon atom of said six-membered aromatic ring(s) is bonded to the benzylic carbon of said —CH 2 C 6 Br 5  group, wherein y, which indicates the number of the —CH 2 C 6 Br 5  groups in said compound, is not less than 1. Processes for preparing the compounds and their use as flame retardants are also disclosed.

This application is a divisional of U.S. application Ser. No. 14/759,174filed Jul. 2, 2015, which is a national phase of InternationalApplication No. PCT/IL2014/000002 filed Jan. 6, 2014, which claims thebenefit of U.S. Provisional Application No. 61/749,330 filed Jan. 6,2013, the entire contents of each of which are hereby incorporated byreference.

The present invention provides a novel class of pentabromobenzylmoiety-containing aromatic compounds having high molecular weight, whichare suitable for use as flame retardants in polymers (e.g., polyamide,polypropylene and acrylonitrile-butadiene-styrene compositions).

Brominated compounds are known to be highly effective as flameretardants, and in many cases they constitute the only viable option forreducing the fire risk of synthetic materials. There exists a need todevelop new, high molecular weight, macro-molecular brominated flameretardants. It is postulated that the higher the molecular weight of thebrominated flame retardant, the lower is its volatility and its abilityto bio-accumulate in living tissues.

Low molecular weight compounds containing a pentabromobenzyl moiety areknown in the art. Pentabromobenzyl acrylate (EP 481126),pentabromobenzyl terephthalate (DE 33 20 333) and pentabromobenzyltetrabromophthalate (EP 47866) have been reported to be useful in flameretarded polymer compositions. Furthermore, poly (pentabromobenzylacrylate) is used as a flame retardant agent in flammable materials.Hereinafter, the pentabromobenzyl group is sometimes described by meansof its molecular structure:

or its molecular formula —CH₂C₆Br₅.

The present invention provides novel compounds containing apentabromobenzyl moiety and possessing highly satisfactory flameretarding properties. These compounds are prepared using electrophilicC-alkylation of different aromatic compounds with pentabromobenzylhalide, in particular bromide, in the presence of Friedel-Craftscatalysts. The pentabromobenzyl group-containing compounds of theinvention have high molecular weight (>1000), their bromine content ispreferably not less than 70%, they are insoluble in water and are alsostable against hydrolysis and/or decomposition.

The compound of the invention has the formula Ar(—CH₂C₆Br₅)_(y), whereinAr indicates a structure comprising one or more six-membered aromaticring(s), characterized in that at least one carbon atom of said sixmembered aromatic ring(s) is bonded to the benzylic carbon of a—CH₂C₆Br₅ group, wherein y, which indicates the number of the —CH₂C₆Br₅groups in the compound of the invention, is not less than 1.

Preferably, Ar contains one six-membered aromatic ring, or two,preferably non-fused, six-membered aromatic rings, and y is at leastequal to twice the number of the six-membered aromatic rings in Ar. Itshould be noted that each of the six membered aromatic ring(s) of whichAr is composed may be substituted, e.g., by alkyl group(s). When Arconsists of two six-membered aromatic rings, then these rings may beeither connected by bridges selected from the group consisting ofalkylene chains, —O— or —S—, or said rings may be fused together.

More specifically, the present invention provides a novel, aromatic,high weight macro-molecular compound which contains a plurality ofpentabromobenzyl moieties, as shown by Formula (I), and/or a mixture ofsuch compounds:

In formula (I), R is H or a linear or branched aliphatic chain, n isindependently an integer from 1 to 3, preferably 2 or 3, m is 0 or 1,such that n+m·n equals y, k is an integer from 1 to 3, X=null, O, S, alinear or branched alkylene, e.g., an alkylene group containing 1 to 10carbon atoms.

The compounds of the invention are prepared by reacting pentabromobenzylhalide, especially pentabromobenzyl bromide (chemically named1-(bromomethyl)-2,3,4,5,6-pentabromobenzene and abbreviated hereinPBBBr) with a starting material which comprises at least onesix-membered aromatic ring, as set out above, in the presence of asuitable Friedel-Crafts catalyst (Lewis acids) such as AlCl₃, AlBr₃,GaCl₃, FeCl₃, SnCl₄, SbCl₃, ZnCl₂, CuCl₂ and HF, preferably AlCl₃. Thus,another aspect of the invention is a process comprising a Friedel-Craftsalkylation reaction of pentabromobenzyl halide with a reactant whichcontains one or more six-membered aromatic rings, in the presence of aFriedel-Crafts catalyst. In the so-formed Ar(CH₂C₆Br₅)_(y) product,there is at least one bond between a carbon atom of an aromatic ring andthe benzylic carbon of the pentabromobenzyl group.

Regarding the pentabromobenzyl bromide starting material, it iscommercially available and produced by ICL-IP or can be prepared bymethods known in the art (e.g., U.S. Pat. No. 6,028,156 and U.S. Pat.No. 7,601,774), according to the route of synthesis involving thearomatic bromination of toluene, for example in halogenated solvent(s),using elemental bromine, in the presence of a Lewis acid catalyst, e.g.AlCl₃, to form pentabromotoluene (abbreviated herein 5-BT), which isthen brominated at the benzylic carbon using elemental bromine and aradical source e.g. azobisizobutiro nitrile, as illustrated by thefollowing scheme (see U.S. Pat. No. 7,601,774):

Regarding the starting material which undergoes aromatic substitutionreaction, namely, electrophilic C-alkylation according to the invention,it contains one six-membered aromatic ring, or two, preferablynon-fused, six-membered aromatic rings. Preferably, the reactant isrepresented by Formula (II):

In formula (II) R is H or a linear or branched aliphatic chain, m is 0or 1, k is an integer from 1 to 3, X=null, O, S, a linear or branchedalkylene, e.g., an alkylene group containing 1 to 10 carbon atoms.

Exemplary starting materials of Formula II include:

Toluene, wherein R═CH₃, k=1, m=0;

Xylene, wherein R═CH₃, k=2, m=0;

Ethylbenzene, wherein R═C₂H₅, k=1, m=0;

Diphenyl ether, wherein R═H, X=0, m=1;

Diphenylmethane, wherein R═H, X═CH₂, m=1; and Diphenylethane, whereinR═H, X═(CH₂)₂, m=1;

The Friedel-Crafts alkylation reaction according to the invention isgenerally carried out in a solvent or a mixture of solvents, e.g., inhalogenated aliphatic hydrocarbon which is preferably selected from thegroup consisting of dichloromethane, dibromomethane (DBM),bromochloromethane and dichloroethane (DCE). The molar ratio between thetwo reactants is suitably adjusted to satisfy the desired degree ofsubstitution on the six membered aromatic ring(s). In general, it isdesired to attach not less than two, and preferably three, —CH₂C₆Br₅groups to each six-membered aromatic ring present in the startingmaterial. The amount of the catalyst, e.g. AlCl₃, is preferably between0.5% wt/wt and 2% wt/wt relative to PBBBr amount. The reaction iscarried out under anhydrous conditions.

The reaction is generally carried out by combining the two reactants inthe solvent under heating in order allow a complete dissolution of thePBBBr (and also of the second reactant, in the event that it is solid atroom temperature), followed by the addition of the catalyst. TheFriedel-Crafts alkylation reaction is accompanied by the generation ofhydrogen bromide. The temperature of the reaction mixture is thenincreased, e.g., to 40° C.-90° C. and the reaction is allowed to reachcompletion. The product is virtually insoluble in the reaction medium,and precipitates almost instantly. In general, the reaction time is from2 to 8 hours. The end of the reaction is indicated by the completeconsumption of the PBBBr (its disappearance may be determined by gaschromatography analysis) or by the cessation of hydrogen bromideevolution.

Thus, the invention also relates to the use of pentabromobenzyl halideas an alkylation reagent in Friedel-Crafts alkylation of the reactantsof Formula II. In a preferred embodiment, the invention provides aprocess comprising a Friedel-Crafts alkylation reaction ofpentabromobenzyl halide, e.g., bromide, with a reactant selected fromthe group consisting of toluene, xylene, ethylbenzene, diphenyl ether,diphenylmethane and diphenylethane in the presence of aluminum chloride,wherein the molar ratio between said pentabromobenzyl bromide and saidreactant is at least equal to twice the number of the six-memberedaromatic rings of said reactant.

The product is isolated from the reaction mixture by means ofconventional techniques. The reaction mixture is repeatedly washed withsodium bisulfite (SBS) solution and water, whereby the excess catalystis destroyed. The solid is then separated from the liquid phase byfiltration. The product can then be treated (slurried) indichloromethane under heating for at least one hour, following which theslurry is cooled and the solid product is collected by filtration, andoptionally washed and dried.

In general, the Friedel-Crafts alkylation of an aromatic compound withpentabromobenzyl bromide according to the invention leads to theformation of a product mixture consisting of several isomers andhomologs [by homologs is meant the homologous series Ar(CH₂C₆Br₅)_(y),in which y=1, 2, 3, and more up to 3+3m, wherein m+1 is the number ofthe six-membered rings in Ar]. The composition of the product mixturecan be roughly determined on the basis of the percentage of bromine.Thus, the variable y, which indicates the number of pentabromobenzylgroups bonded to the six-membered aromatic ring(s), can be a non-integernumber, indicating the average degree of pentabromobenzyl substitutionof the product mixture. For example, Friedel-Crafts alkylation oftoluene with pentabromobenzyl bromide can be controlled to give aproduct with high bromine content, e.g., of about 76%, which correspondsto a product mixture that can be identified by the formulaC₆H_(2.4)(CH₃)(CH₂C₆Br₅)_(2.6), indicating that the predominate homologin the mixture is C₆H₂(CH₃)(CH₂C₆Br₅)₃, but that lower homologs, e.g.,C₆H₃(CH₃)(CH₂C₆Br₅)₂, and possibly also C₆H₄(CH₃)(CH₂C₆Br₅), are alsopresent in the mixture. According to the simplified notation describedin more detail below, the compound C₆H_(2.4)(CH₃)(CH₂C₆Br₅)_(2.6) isnamed Tris(pentabromobenzyl) toluene. However, it should be noted thatthe experimental results reported below demonstrate that the resultantproduct mixture is useful as a flame retardant. In view of the fact thatthe reaction-derived product mixture exhibits said flame retardantproperties, then there is no need to separate the mixture into itsindividual components. Similarly, there is no need to control theconditions of the reaction in order to favor one single desiredcomponent. By varying the reaction conditions, a product containingmaximal pentabromobenzyl groups is obtained.

In one preferred class of the Ar(CH₂C₆Br₅)_(y) compounds of theinvention, Ar is toluene; this class of compounds is represented byFormula I, wherein m=0, R is CH₃ and k is 1, i.e.,pentabromobenzyl-substituted toluene, especiallyTris(pentabromobenzyl)toluene.

In another preferred class of the Ar(CH₂C₆Br₅)_(y) compounds of theinvention, Ar is selected from the group consisting of diphenylether,diphenylmethane and diphenylethane; this class of compounds isrepresented by Formula I, wherein m=1 and R is H. More specifically,this preferred class is also identified herein by Formula III:

wherein X is selected from the group consisting of —O—, —CH₂— and—CH₂—CH₂—, said compounds having bonds between carbon atoms of aromaticrings (of the diphenyloxide or diphenylalkane portion) and the benzyliccarbon of —CH₂C₆Br₅ group, with n1 and n2 being independently 1, 2 or 3,and preferably 2 or 3, such that the bromine content of the compound ispreferably not less than 60%, e.g., in the range from 60 to 78% byweight. More preferred are compounds of Formula III wherein X is—CH₂—CH₂—, having bromine content of not less than 70% by weight, e.g.,in the range from 70 to 78% by weight. Especially preferred compounds ofthe invention are denoted hereinpentakis(pentabromobenzyl)diphenylethane andhexakis(pentabromobenzyl)diphenylethane. As explained above, the productof Formula III consists in fact of a mixture of various —CH₂C₆Br₅homologs. In the simplified notation used herein, a mixture is namedaccording to the homolog which represents the average number of—CH₂C₆Br₅ group per molecule. For example, is the average number is 4.0,then the mixture is named tetrakis(pentabromobenzyl)diphenylethane. Theaverage number of pentabromobenzyl groups per molecule would normally bea mixed number, in which case the average is rounded off viaexcess-rounding, i.e., to the next whole number. The termpentakis(pentabromobenzyl)diphenylethane therefore indicates a mixtureconsisting pentabromobenzyl-substituted diphenylethane molecules, havingan average of between 4 and 5 pentabromobenzyl groups per molecule inthe mixture (4<average≦5). Likewise, the termhexakis(pentabromobenzyl)diphenylethane indicates a mixture consistingof pentabromobenzyl-containing diphenylethane molecules, having anaverage of between 5 and 6 pentabromobenzyl groups per molecule in themixture (5<average≦6). Thus, the notation used in naming the compoundsof the invention is similar to the conventional notation applied innaming ar-brominated diphenyloxide and diphenylethane.

The compounds of the invention are useful as flame retardant agents in aflammable material. Accordingly, another aspect of the present inventionis a flame-retarded formulation which comprises a flammable material(e.g., a polymer) and the novel compounds of the invention of theformula Ar(CH₂C₆Br₅)_(y). Specifically, the compounds of the inventionwere tested in polyamides, polypropylene copolymers andacrylonitrile-butadiene-styrene and were found to demonstrate goodactivity.

The formulation of the invention comprises a flame-retarding effectiveamount of the novel Ar(CH₂C₆Br₅)_(y) compounds of the invention, andespecially the compounds of Formula I and III. The flammabilitycharacteristics of plastic materials are quantifiable according to themethod specified by Underwriter Laboratories standard UL 94. The UL 94ratings are V-0, V-1, and V-2. A material assigned with the V-0 ratingis considered to be the less flammable. A polymeric compositionaccording to the invention which contains at least 5 wt %, andpreferably 10 wt % bromine, would generally satisfy the UL 94 verticalburning test (the entire bromine content being supplied by theAr(CH₂C₆Br₅)_(y) compounds).

Other Conventional additives may also be included in the polymericformulation. For example, an inorganic compound (typically a metaloxide) capable of cooperating with the novel Ar(CH₂C₆Br₅)_(y) flameretardant for retarding the flammability of the polymer is preferablyalso present in the formulation. A preferred example of a suitableinorganic compound, which is generally considered as an “inorganicsynergist”, is antimony trioxide.

An exemplary polymer which can be flame-retarded with the novelAr(CH₂C₆Br₅)_(y) compounds of the invention include polyamide such asNylon 66 [poly(hexamethylene adipamide]. Thus, another aspect of theinvention is a flame-retarded formulation comprising polyamide and aflame retardant of the invention, especially a compound of Formula I orIII, and in particular compounds selected from the group consisting of:pentakis(pentabromobenzyl)diphenylethane; andhexakis(pentabromobenzyl)diphenylethane.

The polyamide-based formulation comprises at least 30% polyamide, e.g.,between 40% and 70% wt %. The polyamide formulation further comprisesreinforcing fillers, namely, glass fibers, which are typicallypre-coated by methods known in the art prior to their use in order toimprove their compatibility with the polyamide matrix. Such modifiedforms of glass fibers are available in the market, e.g., GF Chop Vantage3660 from PPG. The glass fibers comprise filaments with diameter in therange from 2μ to 20μ, and are applied in the form of pieces with lengthin the range from 2 to 10 mm, e.g., from 3 to 4.5 mm. For example, themajor constituents of glass fibers applied for reinforcing polyamide isalumino-borosilicates; such type of glass in known as E-glass. Theconcentration of the glass fibers is from 5% to 40% of the total weightof the polyamide composition.

In addition to the polyamide, the reinforcing fillers, thebromine-containing compound of the formula Ar(CH₂C₆Br₅)_(y) and antimonytrioxide, the polyamide formulation of this invention may furthercontain lubricants, antioxidants (e.g., of hindered phenol or phosphitetype), pigments, UV stabilizers and heat stabilizers. The concentrationof each of the conventional additives listed above is typically in therange between 0.05 and 10 wt %.

The polyamide compositions are produced by melt-mixing the components,e.g., in a co-kneader or twin screw extruder, wherein the mixingtemperature is in the range from 200 to 300° C. For example, thepolyamide, the bromine containing flame retardant of formulaAr(CH₂C₆Br₅)_(y) and the conventional additives (with the exception ofthe glass fibers) are dry blended and the blend is fed to the extruderthroat. The glass fibers are the last to be added, i.e., downstream.

The experimental results reported below indicate that the novelAr(CH₂C₆Br₅)_(y) compounds of the invention demonstrate good activity inreducing the flammability of polypropylene copolymers. Thus, anotheraspect of the invention is a flame-retarded formulation comprising apolypropylene copolymer or impact modified polypropylene and a flameretardant of the invention, especially a compound of Formula I or III,and in particular compounds selected from the group consisting of:pentakis(pentabromobenzyl)diphenylethane; andhexakis(pentabromobenzyl)diphenylethane.

The polypropylene formulation preferably comprises a polypropylenecopolymer in an amount of not less than 50 wt % (relative to the totalweight of the formulation), e.g., from 50 to 85 wt %. Suitablepolypropylene impact copolymer which can be used in the presentinvention can be in the form of block copolymers comprising a firstblock (or phase), which is essentially the polypropylene homopolymercomponent and a second block (or phase), which is an ethylene-propylenecopolymer component. A polypropylene impact copolymer is produced bymeans of sequential polymerization reactions under conditions known inthe art. The first reaction produces the homopolymer component and thesecond reaction produces the copolymer component. Thus, the copolymercomponent is chemically incorporated within the matrix of thehomopolymer component. Different grades of polypropylene impactcopolymer in the form of block copolymers are commercially available(Carmel Olefins, Israel, under the name Capilene® SE 50E, TR 50 and SL50). Impact modified polypropylene can be prepared by admixing apolypropylene homopolymer and a rubber.

The compounds of the invention can be used to reduce the flammability ofeither filler-free or filler-containing polypropylene-basedformulations. When a filler, e.g., talc is used, then its concentrationis preferably in the range from 10-20 wt % relative to the total amountof the formulation. Other additives which can be incorporated in thepolypropylene formulation are as set out above, for example, antimonytrioxide.

The novel Ar(CH₂C₆Br₅)_(y) compounds of the invention also display goodactivity in reducing the flammability of acrylonitrile-butadiene-styrene(ABS). Thus, another aspect of the invention is a flame-retardedformulation comprising ABS and a flame retardant of the invention,especially a compound of Formula I or III, in particular compoundsselected from the group consisting of:pentakis(pentabromobenzyl)diphenylethane; andhexakis(pentabromobenzyl)diphenylethane.

ABS compositions of the invention preferably comprise not less than 50wt % ABS (relative to the total weight of the formulation), e.g., from50 to 85 wt % ABS. The term ABS refers in the context of the presentinvention to copolymers and terpolymers that include the structuralunits corresponding to (optionally substituted) styrene, acrylonitrileand butadiene, regardless of the composition and method of production ofsaid polymers. Characteristics and compositions of ABS are described,for example, in Encyclopedia of Polymer Science and Engineering, Volume16, pages 72-74 (1985). ABS with MFI between 1 and 50 g/10 min (measuredaccording to ISO 1133 at 220° C./10 kg) are used.

The ABS compositions according to the present invention also include oneor more anti-dripping agents such as polytetrafluoroethylene(abbreviated PTFE) in a preferred amount between 0.025 and 0.4 wt %,more preferably between 0.025 and 0.3 wt %, and even more preferablybetween 0.05 and 0.2 wt %. PTFE is described, for example, in U.S. Pat.No. 6,503,988.

Other additives which can be incorporated in the ABS formulation are asset out above, for example, antimony trioxide. Notably, the compounds ofthe invention, especially the compounds of Formula III, and inparticular pentakis(pentabromobenzyl)diphenylethane; andhexakis(pentabromobenzyl)diphenylethane, exhibit excellent utility inABS even in the presence of a small amount of antimony trioxide, e.g.,less than 1.8 wt % Sb₂O₃ relative to the total weight of theformulation. ABS formulation comprising a compound of Formula III, asidentified above, and antimony trioxide, wherein the weight ratiobetween the compound of Formula III and antimony trioxide is above 5:1,and preferably above 7:1, forms another aspect of the invention.

The plastic formulations set forth above are readily prepared by methodsknown in the art. The various ingredients of the formulation are blendedtogether, according to their respective amounts. The ingredients may befirst dry blended using suitable mixing machines, such as Henschelmixer. The resulting mixture may then be processed and compounded toform homogeneous pellets, for example, by using a twin screw extruder.The pellets obtained are dried, and are suitable for feed to an articleshaping process such as injection molding. Other blending and shapingtechniques can also be applied. Articles molded from the polymerformulations form another aspect of the invention.

EXAMPLES Example 1 Reaction of Toluene with PBBBr

DBM (200 ml), PBBBr (62.2 g, 0.11 mol) and toluene (3.7 g, 0.04 mol)were placed into a 500 ml flask fitted with a mechanical stirrer,thermometer, condenser and N₂ inlet. The mixture was heated to 70° C.until the PBBBr had dissolved. AlCl₃ (0.7 g, 0.005 mol) was added andthe vigorous formation of HBr started. The mixture was heated at 80° C.for 6 hours until the PBBBr disappeared (by GC). The reaction mixturewas washed three times with water (3×120 ml) and SBS (1.5 ml, ˜28%aqueous solution) taking 20 minutes for each washing. After that, thesolid was filtered out and re-slurried with DCM (2×200 ml) at 40° C.,for one hour (each reslurry). The reaction mixture was cooled to 20° C.and the solid was filtered off and dried in an oven at 150° C. underreduced pressure for 24 hours, to give 42.7 g, corresponding to ˜75%yield, based on PBBBr. According to elemental analysis, the content ofbromine is about 76% (parabomb), corresponding to ˜2.7 PBBBr moleculesper molecule of toluene. The product of this example is represented bythe formula C₆H_(2.3)(CH₃)(CH₂C₆Br₅)_(2.7) and is namedTris(pentabromobenzyl)toluene.

Example 2 Reaction of Toluene with PBBBr

The procedure of Example 1 was repeated, but using PBBBr (56.6 g, 0.1mol), toluene (4.6 g, 0.05 mol), AlCl₃ (2.8 g, 0.02 mol) anddichloroethane (200 ml) as the solvent. The weight of the product was49.5 g, corresponding to ˜86% yield, the content of bromine is about75.0%.

Example 3 Reaction of Diphenyloxide with PBBBr

The procedure of Example 1 was repeated, but using PBBBr (169.8 g, 0.3mol), diphenyloxide instead of toluene (8.5 g, 0.05 mol) and AlCl₃ (2.8g, 0.02 mol). The weight of the product was 115.7 g, corresponding to˜75% yield, the content of bromine is about 78%.

Example 4 Reaction of Diphenylmethane with PBBBr

The procedure of Example 1 was repeated, but using PBBBr (68 g, 0.12mol), diphenylmethane instead of toluene (3.3 g, 0.02 mol) and AlCl₃(1.4 g, 0.01 mol). The weight of the product was 41.8 g, correspondingto ˜68% yield, the content of bromine is about 77.4%.

Example 5 Reaction of Diphenylethane with PBBBr

The procedure of Example 1 was repeated, but using diphenylethane (3.65g, 0.02 mol) instead of toluene. The weight of the product was 35.6 g,corresponding to ˜63% yield, the content of bromine is about 77%.

Example 6 Reaction of Diphenylethane with PBBBr

The procedure of Example 5 was repeated, but using dichloroethane as asolvent. The weight of the product was 46.7 g, corresponding to ˜83%yield, the content of bromine is about 77%. The product ishexakis(pentabromobenzyl) diphenylethane.

Example 7 Reaction of Diphenylethane with PBBBr

DCE (1600 ml), PBBBr (805.6 g, 1.42 mol) and diphenylethane (57.70 g,0.317 mol) were placed into a 2000 ml glass reactor fitted with amechanical stirrer, thermometer, condenser and N₂ inlet. The mixture washeated to 70° C. and AlCl₃ (4.5 g, 0.17 mol) was added portionwiseduring ˜3 hours. Then the mixture was heated for an additional hour at65-75° C. until the PBBBr disappeared (by GC). The reaction mixture waswashed three times with water (3×1000 ml) at ˜60° C. and SBS (20 ml,˜28% aqueous solution) taking 20 minutes for each washing. After that,the solid was filtered off at 40-50° C., washed with 200 ml DCE, anddried in an oven at 150° C. under reduced pressure for 20 hours, to give738 g, corresponding to an ˜98% yield. The content of bromine was ˜75%.The product is pentakis(pentabromobenzyl)diphenylethane.

Examples 8 and 9 (of the Invention) and 10 (Comparative) V-0 Rated FlameRetarded Formulations of Polyamide 66

The products of Examples 1 and 7 were tested as flame retardants (FR) innylon compositions according to the procedure described below. Acommercially available polymeric flame retardant, FR-803P, was alsotested for the purpose of comparison.

Ingredients Used to Prepare the Compositions

The materials used for preparing the nylon compositions are tabulated inTable 1:

TABLE 1 TRADE NAME (PRODUCER) GENERAL INFORMATION FUNCTION Aculon S 223DPolyamide 66 (contains Plastic matrix (DSM) nucleating agent, moldrelease agent & lubricant) FR-803P (ICL-IP) Brominated polystyrene FRProduct of Example 1 Tris(pentabromobenzyl)toluene FR Product of Example7 Pentakis(pentabromobenzyl) FR diphenylethane GF ChopVantage 3660 Glassfibers Reinforcing (PPG) filler AO M-0112 Antimony trioxide masterbatch,FR-synergist (Kafrit) 77%, universal grade. Acrawax C Multifunctional,nitrogen- Antioxidant & (Lonza) containing, hindered phenol heatstabilizer Irganox B1171 (Ciba) N,N′ ethylene bisstearamide Lubricant CaStearate Ca-stearate Lubricant

Preparation of the Compositions and Test Specimens

The compounding was performed in a twin-screw co-rotating extruder ZE25with L/D=32 (Berstorff). PA 66 pellets (which were dried overnight at80° C. in a vacuum oven), the flame retardant, Acrawax C, Irganox B1171and Ca stearate were weighed on Sartorius semi-analytical scales withsubsequent manual mixing in plastic bags. The blend was then fed viafeeder N^(o) 1. The glass fiber was fed in via feeder N^(o) 3 to the 5thsection of the extruder via a lateral feeder. The compounding conditionsare presented in Table 2. The extruded strands were cooled in a waterbath and pelletized. The obtained pellets were dried in a vacuum at 80°C. overnight.

TABLE 2 PARAMETER UNITS Set values Read values Feeding zone temperature(T₁) ° C. T₂ ° C. 250 234-256 T₃ ° C. 270 269-285 T₄ ° C. 270 259-287 T₅° C. 270 267-270 T₆ ° C. 270 262-279 T₇ (vent) ° C. 275 265-286 T₈ ° C.275 268-293 T₉ ° C. 280 264-281 Temperature of melt ° C. 260-281 Screwspeed RPM 300 Feeding rate Kg/h  12

The dried pellets were injection molded into 1.6 thick test specimensusing Allrounder 500-150 from Arburg. The conditions of the injectionmolding are tabulated in Table 3 below:

TABLE 3 PARAMETER UNITS Set values T₁ (Feeding zone) ° C. 240 T₂ ° C.260 T₃ ° C. 285 T₄ ° C. 290 T₅ (nozzle) ° C. 295 Mold temperature ° C.90 Injection pressure bar 1300 Holding pressure bar 700-900 Backpressure bar 10 Injection time sec 40 Holding time sec 6 Cooling timesec 1 Injection speed ccm/sec 50

The specimens were conditioned for at least 48 hours at 23° C., and werethen subjected to the tests outlined below.

Tests Flammability Test

The flammability test was carried out according to theUnderwriters-Laboratories standard UL 94, applying the vertical burn onspecimens of 1.6 mm thickness.

Mechanical Properties

Impact strength was measured using the Izod notched test according toASTM D-256, using pendulum impact tester type 5102 (Zwick); Tensileproperties (tensile strength, tensile modulus, elongation at yield andelongation at break) were measured in Zwick/Roell Z010 material testingmachine according to ASTM D-638 (type 2 dumbbells were used, with thespeed of test being 5 mm/min).

Thermal Properties

HDT (heat distortion temperature; this is the temperature at which apolymer sample deforms under a specific load) was measured according toASTM D-648-72 with load of 18.5 kg/cm² and heating rate 2° C./min; MFI(melt flow index) was determined according to ASTM D1238. Thecompositions tested and the results are set out in Table 4.

TABLE 4 Example 8 9 10 FR Product of Product of FR 803P Example 1Example 7 PA 66 (Aculon S 223-D) 46.3 51.3 43.5 GF ChopVantage 3660 3030 30 FR 16.9 13.3 19.7 AO M-0112 6.3 4.8 6.2 Acrawax C 0.2 0.2 0.2Irganox B1171 0.2 0.2 0.2 Ca-stearate 0.2 0.2 0.2 Br (calculated) 13 1013 Sb₂O₃ (calculated) 4.8 3.7 4.8 Br/Sb₂O₃ (calculated) 2.7 2.7 2.7Total flaming time 10 19 32 Max. flaming time 1 5 8 No. of dripping 0 50 No. of cotton ignition 0 0 0 Rating V-0 V-0 V-0 Izod Impact 104 103111 Tensile strength 150 150 143 Elongation at yield 2.6 3.3 3Elongation at break 4.2 4.7 3.3 Tensile modulus 10747 9948 10044 MFI 1129 7 HDT 226 231 225

Examples 11-13 V-2 and V-0 Rated Flame Retarded Formulations ofPolypropylene Impact Copolymers

The product of Example 7, pentakis(pentabromobenzyl) diphenylethane, wastested in compositions of polypropylene impact copolymers according tothe procedure described below.

Ingredients Used to Prepare the Compositions

The materials used for preparing the polypropylene compositions aretabulated in Table 5:

TABLE 5 Component (manufacturer) GENERAL DESCRIPTION FUNCTION PPCapilene polypropylene impact copolymer plastic matrix SL-50 (Caol)Product of Pentakis(pentabromobenzyl) flame retardant Example 7diphenylethane FR00112 Antimony trioxide masterbatch which FR synergist(Kafrit) contains 80 wt % Sb₂O₃ Lotalc Talc Filler Irganox B 225Antioxidant/processing stabilizer Antioxidant & (Ciba) Irganox1010:Irgafos 168 1:1 blend heat stabilizer.

Preparation of Compositions and Test Specimens

The ingredients were pre-mixed, and fed via volumetric feeder #2 to theport of a twin-screw co-rotating extruder ZE25 with L/D=32 fromBerstorff. Specific conditions are presented in Table 6:

TABLE 6 PARAMETER UNITS Set values Screws Medium shear A Feeding zone °C. no temperature (T₁) heating T₂ ° C. 160 T₃ ° C. 180 T₄ ° C. 200 T₅ °C. 200 T₆ ° C. 210 T₇ ° C. 210 T₈ ° C. 220 T₉ ° C. 230 Screw speed RPM350 Feeding rate Kg/h 15

The strands produced were pelletized in a pelletizer 750/3 from AccrapakSystems Ltd. The resultant pellets were dried in a circulating air ovenat 80° C. for 3 hours. The dried pellets were injection molded into testspecimens using Allrounder 500-150 from Arburg as tabulated Table in 7.

TABLE 7 PARAMETER UNITS Set values T₁ (Feeding zone) ° C. 50 T₂ ° C. 220T₃ ° C. 220 T₄ ° C. 220 T₅ (nozzle) ° C. 230 Mold temperature ° C. 40Injection pressure bar 600 Holding pressure bar 450 Back pressure bar 60Holding time sec 5 Cooling time sec 18 Mold closing force kN 500 Fillingvolume (portion) ccm 38 Injection speed ccm/sec 30

The specimens were conditioned for one week at 23° C., and were thensubjected to the tests outlined below.

Tests Flammability Test

The flammability test was carried out according to theUnderwriters-Laboratories standard UL 94, applying the vertical burn onspecimens of 1.6 mm thickness.

Mechanical Properties

Impact strength was measured using the Izod notched test according toASTM D-256-81, using pendulum impact tester type 5102 (Zwick); Tensileproperties (tensile strength, tensile modulus, elongation at break) weremeasured in Zwick/Roell Z010 material testing machine according to ASTMD-638-95 (v=5, test speed 10 mm/min).

Thermal Properties

HDT (heat distortion temperature; this is the temperature at which apolymer sample deforms under a specific load) was measured according toASTM D-648-72 with load of 1820 kPa and heating rate of 120° C./hour;the instrument is HDT/Viact-plus from Davenport, Lloyd instruments. MFI(melt flow index) was determined according to ASTM D1238 (230° C./2.16kg); the instrument is Meltflixer 2000 from Thermo Hake. Thecompositions tested and the results are set out in Table 8.

TABLE 8 Example 10 11 12 Composition (by weight %): Polypropylene impactcopolymer 56.7 55.1 53.3 FR of Example 7 29.3 22.7 24.0 Lotalc 25 15.015.0 Antimony trioxide masterbatch 13.8 7.1 7.5 Irganox B 225 0.2 0.20.2 Bromine content, % calculated 22.0 17.0 18.0 Antimony trioxide, %calculated 11.0 5.7 6.0 Bromine/Sb₂O_(3 ratio) 2.0 3.0 3.0 PropertiesFlammability test: UL-94 vertical burning test at 1.6 mm thicknessMaximal flaming time (sec) 6 10 6 Total Flaming time (sec) 16 42 28Number of Specimens dripped 5 5 5 Number of cotton ignition 0 1 0 RatingV-0 V-2 V-0 Mechanical Properties Impact strength (J/m) 27 nd 28 Tensilestrength (N/mm2) 17.2 nd 18 Elongation at break (%) 64 nd 27 Tensilemodulus (N/mm2) 1490 nd 2060 Thermal properties HDT (° C.) 63 nd 67 MFI(g/10 min) 4.1 nd 3.5

Example 14 V-0 Rated Flame Retarded Formulation of ABS

The product of Example 7, pentakis(pentabromobenzyl) diphenylethane, wastested in compositions of ABS according to the procedure describedbelow.

Ingredients Used to Prepare the Compositions

The materials used for preparing the ABS compositions are tabulated inTable 9:

TABLE 9 Component (manufacturer) GENERAL DESCRIPTION FUNCTION ABS MagnumAcrylonitrile-butadiene-styrene plastic matrix 3404 (Styron) copolymerProduct of Pentakis(pentabromobenzyl) flame retardant Example 7diphenylethane FR00112 Antimony trioxide masterbatch which FR synergist(Kafrit) contains 80 wt % Sb₂O₃ Hostaflon 2017 PTFE Anti-dripping(Dyneon) agent Irganox B 225 Phenol:Phosphite 3:1 based stabilizerAntioxidant & (Ciba) heat stabilizer.

Preparation of Compositions and Test Specimens

The compounding was performed in a twin-screw co-rotating extruder ZE25with L/D=32 from Berstorff. Specific conditions are presented in Table10.

TABLE 10 PARAMETER UNITS Set values Screws Medium shear A Feeding zone °C. no temperature (T₁) heating T₂ ° C. 180 T₃ ° C. 200 T₄ ° C. 210 T₅ °C. 210 T₆ ° C. 210 T₇ ° C. 220 T₈ ° C. 230 T₉ ° C. 240 Screw speed RPM350 Feeding rate Kg/h 15

The strands produced were pelletized in a pelletizer 750/3 from AccrapakSystems Ltd. The resultant pellets were dried in a circulating air ovenat 80° C. for 3 hours. The dried pellets were injection molded into testspecimens using Allrounder 500-150 from Arburg as tabulated in Table 11.

TABLE 11 PARAMETER UNITS Set values T₁ (Feeding zone) ° C. 210 T₂ ° C.215 T₃ ° C. 220 T₄ ° C. 230 T₅ (nozzle) ° C. 230 Mold temperature ° C.40 Injection pressure bar 900 Holding pressure bar 800 Back pressure bar50 Holding time sec 7 Cooling time sec 10 Mold closing force kN 500Filling volume (portion) ccm 38 Injection speed ccm/sec 25

The specimens were conditioned for one week at 23° C., and were thensubjected to the tests outlined below.

Tests Flammability Test

The flammability test was carried out according to theUnderwriters-Laboratories standard UL 94, applying the vertical burn onspecimens of 1.6 mm thickness.

Mechanical Properties

Impact strength was measured using the Izod notched test according toASTM D-256-81; Tensile properties (tensile strength, tensile modulus,elongation at break) were measured in Zwick/Roell Z010 material testingmachine according to ASTM D-638-95 (v=50 mm/min).

Thermal Properties

HDT was measured according to ASTM D-648-72 with load of 1820 kPa andheating rate of 120° C./hour; the instrument is HDT/Vicat-plus fromDavenport, Lloyd instruments. MFI (melt flow index) was determinedaccording to ASTM D1238 (200° C./5 kg); the instrument is Meltflixer2000 from Thermo Hake. The compositions tested and the results are setout in Table 12.

TABLE 12 Example 14 Composition (by weight %): ABS 80.4 FR of Example 717.4 Antimony trioxide masterbatch 1.9 PTFE 0.1 Irganox B 225 0.2Bromine content, % calculated 13.0 Antimony trioxide, % calculated 1.5Bromine/Sb₂O₃ ratio 8.66 Properties Flammability test: UL-94 verticalburning test at 1.6 mm thickness Maximal flaming time (sec) 9 TotalFlaming time (sec) 24 Max glowing time 0 Number of specimens whichdripped 0 Number of cotton ignition 0 Number of specimen burned up tothe clamp 0 Rating V-0 Mechanical Properties Impact strength (J/m) 104Tensile strength (N/mm2) 39 Elongation at break (%) 13 Tensile modulus(N/mm2) 2161 Thermal properties HDT (° C.) 78 MFI (g/10 min) 11.7

1) A process for preparing a compound of the formula Ar(—CH₂C₆Br₅)_(y),wherein Ar indicates a structure comprising one or more six-memberedaromatic ring(s), —CH₂C₆Br₅ is the pentabromobenzyl group and yindicates the number of the —CH₂C₆Br₅ groups in the compound, wherein yis not less than 1, said process comprises a Friedel-Crafts alkylationreaction of pentabromobenzyl halide with a reactant, wherein saidreactant contains one or more six-membered aromatic rings, in thepresence of a Friedel-Crafts catalyst, to form said Ar(CH₂C₆Br₅)_(y)compound having at least one bond between a carbon atom of an aromaticring and the benzylic carbon of the pentabromobenzyl group. 2) A processaccording to claim 1, wherein not less than two —CH₂C₆Br₅ groups areattached to each six-membered aromatic rings present in the reactant. 3)A process according to claim 2, wherein three —CH₂C₆Br₅ groups areattached to each six-membered aromatic rings present in the reactant. 4)A process according to claim 1, wherein the Friedel-Crafts catalyst isselected from the group consisting of AlCl₃, AlBr₃, GaCl₃, FeCl₃, SnCl₄,SbCl₃, ZnCl₂, CuCl₂ and HF. 5) A process according to claim 1, whereinthe reactant is a compound of Formula (II):

wherein R is H or a linear or branched aliphatic chain, m is 0 or 1, kis an integer from 1 to 3, X=null, an alkylene group containing 1 to 10carbon atoms, O and S. 6) A process according to claim 5, wherein thereactant is selected from the group consisting of: Toluene, wherein inFormula II m=0, R═CH₃, k=1; Xylene, wherein in Formula II m=0, R═CH₃,k=2; Ethylbenzene, wherein in Formula II m=0, R═C₂H₅, k=1; Diphenylether, wherein in Formula II m=1, R═H, X=0; Diphenylmethane, wherein inFormula II m=1, R═H, X═—CH₂—; and Diphenylethane, wherein in Formula IIm=1, R═H, X═—(CH₂)₂—. 7) A process according to claim 6, comprising aFriedel-Crafts alkylation reaction of pentabromobenzyl bromide with areactant selected from the group consisting of toluene, xylene,ethylbenzene, diphenyl ether, diphenylmethane and diphenylethane in thepresence of aluminum chloride, wherein the molar ratio between saidpentabromobenzyl bromide and said reactant is at least equal to twicethe number of the six-membered aromatic rings of said reactant. 8) Aprocess according to claim 1, wherein the Friedel-Crafts alkylationreaction takes place in a solvent which is halogenated aliphatichydrocarbon. 9) A product mixture consisting of homologous series of theformula Ar(—CH₂C₆Br₅)_(y), where Ar indicates a structure comprising oneor more six-membered aromatic ring(s) and —CH₂C₆Br₅ indicates apentabromobenzyl group, wherein the benzylic carbon of said —CH₂C₆Br₅group is bonded to a carbon atom of said six-membered aromatic ring(s),and further wherein said homologous series comprises the compound AreCH₂C₆Br₅)₃m+3, where m+1 is the number of the six-membered aromaticrings in Ar.